Newman adds:
Bake at 250f in an oven on an upside down cookie sheet for 20 minuets and then peel. No foams soaked with boiling hot water and no foam paste inside the tires. It the rubber does not come right loose bake another 15 minuets. Follow with a good air freshener.

HoBao suggests:
Go to the local chain store and buy a litre of Acetone. It is usually kept in the same area as the Methylated Spirts and Turpentine etc.
Pour acetone into bowl deep enough to submerge the wheel and trye. Place in the item and leave for about 1 hour. Tyre will fall away from rim. The foams can be used again if washed out in soapy water and dried as soon as they are removed.
Be careful and wear gloved when handling Acetone.
This works for me and is a no mess no fuss cheap way of removing tyres.

Neil adds:
Assuming that the tyres are completely worn out, why not just cut them to get the foam out that way you won't have to mess about washing the acetone out of it.

Newman answers:
Now Neil, believe it or not as far fetched as this may sound. It can and has happened more than once where a person might get distracted or confused and glue directional tires on to the rims all in the same direction. So then you have the option of either running mismatched tire patterns or you try to get the tires off so you can reverse and reglue them. There is also the odd case of when you break the center out of one wheel but you have a near new set of tires. Rather than buy another brand new set of tires and wheels you gotta try to save that tire.